1. Field of the Invention
The present invention relates to a mold for manufacturing a skin covered foamed plastic seat and, more particularly, to such a mold for a seat incorporating holes at desired positions in a process of manufacturing.
2. Description of the Background Art
Car seat cushions and seat backs have been made of a pad member covered by a skin cover. The pad member and the skin cover used to be manufactured separately and combined together later, but it has become fashionable to manufacture a skin covered pad member altogether by making the foamed plastic inside the skin cover placed over a molding surface, so that the process of combining at a later time may be omitted.
In such a skin covered foamed plastic seat, holes for inserting such things as head rest supports and rotation hinge supporters are often incorporated in the process of manufacturing.
One of the most common problems encountered in such a process of manufacturing a skin covered pad member is the leakage of the liquid foam resin which will become a pad member onto the front surface of the skin cover.
In general, the skin cover is made from air impermeable materials, but even when an air permeable front surface skin is used, a backing material or wadding which is air impermeable can be used. This wadding may be effective enough to prevent the leakage of the liquid foam resin, but for a skin covered pad member such as that to be used for a rear seat cushion which is required to have holes for the seat belts, the problem of the leakage of the liquid foam resin can be prominent.
More specifically, the required holes on the skin covered pad member are manufactured by using a mold such as that shown in FIG. 1, comprising an upper mold 1 and a lower mold 2 to be assembled with the upper mold having a bossing 3 corresponding to the holes to be made on the skin covered foamed plastic seat. Now, when the skin cover 4 comprising the surface skin 6a and the wadding 6b is placed over the lower mold 2, there is usually a small space between the bossing 3 and the edge 4a of the skin cover 4, so that when the liquid foam resin is poured into the mold, the leakage of the liquid foam resin through such a space between the bossing 3 and the edge 4a of skin cover 4 occurs, and the leaked liquid foam resin will be foamed on the front surface of the skin cover 4 and will have to be removed afterwards. This leaked foam resin after the foaming of the liquid foam resin is not easily removable, so that the leakage of the liquid foam resin can severely affect the manufacturing efficiency.
Even when the bossing 3 is made to fit with the edge 4a of the skin cover 4 tightly at the beginning of the manufacturing process, the force due to the expansion of the liquid foam resin in the foaming process will tend to pull the skin cover 4 away from the bossing 3 and can create a space between the bossing 3 and the edge 4a of the skin cover 4, so that the leakage cannot be prevented.
A conventional method to deal with this situation has been sealing of the edge 4a of the skin cover 4 by tapes, but because of the same force due to the expansion of the liquid foam resin in the foaming process, such a sealing is often not very secure, so that it is not considered as an effective protection against this type of leakage.